As it is well known, an optical code is information coded in the color and possibly in the number and in the relative size of a plurality of elements. The linear codes of the bar type, for example, contain an alternate sequence of typically black bars and of typically white spaces, each having a multiple width of a basic width. Two-dimensional optical codes contain a grid of elements of constant shape and size, but of two or more different colors. However, also alphanumeric characters generally form part of the term “optical code” as used in the present description and in the appended claims.
Optical code readers generally comprise means for illuminating the optical code and means for detecting the light diffused by the optical code and for generating an electrical signal the amplitude and phase of which are representative of the color and size of the optical code elements. The electrical signal is properly processed e.g. through filters, amplifiers and digitizers, to obtain a binary representation of the optical code, which is then decoded, in order to obtain the information associated with the specific optical code being read. Part of the optical code reading, typically the decoding, can be transferred to a host processor.
The invention relates more particularly to optical code readers of the imager type, wherein the entire code, or the entire width of a linear code, is simultaneously illuminated, and the light diffused by the entire illuminated optical code is collected and detected through a photodetector device or sensor of the linear or matrix type, respectively in the case of linear and two-dimensional optical codes.
In order to collect the diffused light onto the sensor, the imager readers typically comprise a receiving optics. In the optical code readers it is appropriate to provide for a focusing capability, i.e. that the distance between the receiving optics and the sensor is settable, to allow the reading of optical codes at different distances.
In the imager readers it is also appropriate for the electrical signal to be influenced neither by the non uniformity in the illumination of the different regions of the optical code, e.g. caused by the emitting characteristics of the illumination source/s used, nor by a non-uniform response among the different sensitive regions of the sensor, e.g. caused by the different angles under which they are illuminated by the light diffused by the optical code.
It is therefore known to associate with the light source/s illumination optics that corrects said non uniformity, as for example in GB 2 225 659 A.
Such a document teaches to associate with each of a pair of LEDs (Light Emitting Diode) a lens or a lens portion to focus the light in a direction parallel to the optical code, and a lens or a lens portion to focus the light in a direction orthogonal to the optical code, in order to obtain a thin strip-like illumination line, wherein the illumination at the ends of the strip can be stronger than at the centre. The reader of such document, however, provides for the optical code to be placed in a predetermined position with respect to the reader.
An optical code reader of the imager type includes: at least one non-collimated light source having an illumination optics associated therewith including at least one lens; and a photodetector device having a receiving optics associated therewith including at least one lens, wherein the at least one lens of the illumination optics and the at least one lens of the receiving optics are displaceable together to change their distance from the at least one light source and from the photodetector device, respectively.
These and other aspects and advantages of the reader according to the invention will be better understood from the following detailed description of some embodiments, made with reference to the accompanying drawings, given merely as a not limiting example. The drawings are diagrammatic representations, wherein the hatching filling the different components is used simply for better differentiating them from each other, and is neither indicative of section planes nor of constituent materials. Moreover, some components are shown as if they were transparent, again, only in order to better show the components behind.